This pull request improves how query objects are merged, specifically by flattening nested $and branches so that $and never contains another $and. This makes the resulting queries simpler and avoids unnecessary nesting, which can help with readability and downstream processing. The changes include a new utility function, updates to the merge logic, and additional tests to verify the new behavior.

Improvements to query merging:

• Added a new utility function flattenAndBranches in flatten-and-branches.ts that recursively hoists nested $and branches, ensuring that $and never contains another $and.
• Updated mergeQueryBodies in merge-query-bodies.ts to use flattenAndBranches when merging with $and, so that merged queries are always flat with respect to $and. [1] [2]

Testing and validation:

• Added comprehensive unit tests for flattenAndBranches to verify its behavior with various nesting scenarios.
• Added new test cases in merge-query-bodies.ts and merge-query.util.test.ts to ensure that merging queries with nested $and branches produces the expected flat structure. [1] [2]